diff --git a/astrbot/core/agent/tool.py b/astrbot/core/agent/tool.py
index 04a47b35f..c2536708e 100644
--- a/astrbot/core/agent/tool.py
+++ b/astrbot/core/agent/tool.py
@@ -285,6 +285,9 @@ class ToolSet:
                     prop_value = convert_schema(value)
                     if "default" in prop_value:
                         del prop_value["default"]
+                    # see #5217
+                    if "additionalProperties" in prop_value:
+                        del prop_value["additionalProperties"]
                     properties[key] = prop_value
 
                 if properties: